Cities such as Chicago, Minneapolis and Milwaukee are at risk for a severe weather outbreak, forecasters said.

A tornado watch is in effect until 8 p.m. Thursday, May 15. The National Weather Service issued the watch for 21 Minnesota counties, including Stearns, Benton and Sherburne counties. The watch was issued shortly after 2:30 p.m. Thursday.

"Storms may initially form as individual supercells that would pose a higher risk for strong tornadoes (EF2+) and very large hail (up to baseball size)," the bulletin reads. "The storms would likely form into a single line of storms posing a higher risk for hurricane force winds and tornadoes."